Catalytic oxidation of peroxy salts

ABSTRACT

Transition metal ions have the ability to increase the oxidation performance of the inorganic peroxy salts at room temperature by possibly lowering their activation energy or by producing more reactive free radicals. When two transition metal salts are used together to decompose dipersulfate, it provides synergistic oxidation activity, better than obtained by dipersulfate or dipersulfate with either copper or zinc alone. The transition metals mentioned are the water soluble salts of copper and zinc. Oxidation performance of sodium dipersulface in presence of catalytic amount of copper and zinc salts was determined by measuring the destruction of crystal violet dye at a wavelength of 589 nm.

REFERENCE TO A RELATED APPLICATION

The present application claims the benefit of the provisional patentapplication 60/377,968 filed May 7, 2002, which is relied on andincorporated herein by reference.

FIELD OF INVENTION

The present invention relates generally to a method and composition fortreatment of water system to inhibit microbial and algal growth. Inparticular, this invention relates to metal activated non-chlorineoxidizer based composition with or without a chlorine oxidizer, aclarifier and a biocide to treat water body. More particular, theinvention relates to treatment of water systems such as swimming pools,spas, hot tubs, cooling water or any water body that is subject to thegrowth of micro-organisms.

INTRODUCTION AND BACKGROUND

Many water use applications like swimming pools, spas, hot tubs, coolingtowers, process water, and the like, require a constant residual ofbiocide chemicals to control bacterial and algal populations, in orderto have sanitary water safe for the users, operators, and servicepersonnel. Typical organisms that will grow in the water in such systemsinclude Chlorococcum, Chlorella, Cledaphora, Microcystis, Oscilratoris,Spirosyra, Olaothrisx, Vanetteria, and Aspergilles flavus. Theprevention or inhibition of growth of these micro-organisms in watersystems has been a problem.

It is customary to treat water systems with one or more sanitizersand/or sanitizer/oxidizer combinations to control the growth ofmicro-organisms. The sanitizers most commonly used to control the growthof micro-organisms are chemicals that generate hypochlorite orhypobromite species when dissolved in water. There are many hypochloritegenerating chemicals, with the more common ones being chlorine gas,alkali metal hypochlorites such as sodium hypochlorite, alkaline earthmetal hypochlorites such as calcium hypochlorite and lithiumhypochlorite, halogenated hydantoins and chlorinated isocyanuric acidderivatives such as sodium or potassium dichloro-s-triazinetrione.

The most common sanitizers that are used in applications that directlycontact people (swimmers, waders, or bathers, etc) are oxidizingsanitizers that release hypochlorous acid (chlorine) into the water. Itis common practice to periodically “shock” or “oxidize” the water byadding a significant amount of an oxidizing chemical to water to destroyinorganic and organic contaminants. Shock products are largely solidproducts. In some cases, chlorine- or halogen-releasing products areperiodically used to oxidize contaminants, shock and kill bacteria andalgae.

It is highly desirable to have multi-functional oxidizer or shockproducts for use in water treatment applications. Examples of suchpatented technology relating to mixtures of a chlorine source, anon-halogen oxidizer source, and other additives are Pat. Nos.5,478,482, 5,514,287, and 5,670,059. The research disclosed in thesepatents show a synergy between sodium dipersulfate and sodiumdichloro-s-triazinetrione.

Prior art teaches that the oxidation performance of sodium dipersulfatecompound is greatly dependent on temperature. It is more effective whenthe temperature is at or above 60° C. and experience a decreasedreactivity at the lower temperatures.

Although, the prior patent indicates that blends of sodium dipersulfateand dichloro-s-triazinetrione have superior oxidization properties whencompared to the individual components, it is desirable to furtherimprove the oxidation properties of sodium dipersulfate in theformulations with dichloro-s-triazinetrione especially at ambienttemperatures.

Since the swimming pool water temperature is generally ambient, a largequantity of peroxy compound will have to be used to provide the desiredbenefits. The dependence of peroxy compound on temperature andconcentration is practically and economically significant. As aconsequence, there is much interest in catalyzing or activating peroxycompounds, which will increase the oxidation performance of thesecompounds by allowing them to be effective at ambient temperatures. Suchsubstances are generally referred to in this art as catalysts or peroxycompound catalysts or activators.

U.S. Pat. No. 3,702,298, issued to Zsoidos et al. on Nov. 7, 1972,teaches a method for treating swimming pools with a combination of aperoxy salt, such as peroxymonosulfuric acid and copper salt. However,no prior art teaches the use of two transition metal salts incombination to activate sodium dipersulfate oxidation.

It is, therefore, an object of this invention to provide an improvedperoxy salts based formulation catalyzed by two transition metal fortreatment of water system. This formulation may or may not additionallycontain chlorine releasing chemicals, a clarifier and a biocide.

SUMMARY OF THE INVENTION

The present invention relates to treatment of water including swimmingpool, spa, hot tubs, cooling towers, process water, etc. The inventionparticularly relates to improving oxidation properties to better allowoxidizing sanitizers to control the microbial growth in these watersystems. In addition, since the oxidation acceleration additives mayalso have algistatic or algicidal functions, this discovery betterteaches how to include a chemical that provides sustained algicidalproperties into an oxidizer product. It has been discovered for thefirst time that the oxidation performance of sodium dipersulfate inpresence of water soluble copper and zinc salts in combination providessynergistic oxidative activity, better than that obtained bydipersulfate or dipersulfate catalyzed by copper or zinc salts alone.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further understood with reference to theaccompanying drawings, wherein

FIG. 1 is a graph showing the effect of copper sulfate on oxidationperformance of sodium dipersulfate (DPS);

FIG. 2 is a graph showing the effect of zinc sulfate on oxidationperformance of sodium dipersulfate (DPS);

FIG. 3 is a graph showing the synergistic effect of copper sulfate andzinc sulfate on oxidation performance of sodium dipersulfate (DPS);

FIG. 4 is a graph comparing the effect of metal salts on oxidationperformance of multi-component water treatment formulations; and

FIG. 5 is a graph comparing the effects of copper sulfate andcombination of copper sulfate+zinc sulfate on oxidation performance ofmulti-component water treatment formulations.

DETAILED DESCRIPTION OF INVENTION

The water treatment formulation according to the present invention cancomprise a halogen source, a non-halogen oxidizer, a clarifying agentand a metal ion/s as a catalyst for non-halogen oxidizer activation.This composition may optionally contain a boron source material also.

The halogen source material can be selected from sodium or potassiumdichloro-s-triazinetrione, trichloro-s-triazinetrione, calciumhypochlorite, lithium hypochlorite, brominated hydantoins and brominatedglycouril.

The non-halogen oxygen donor material can be selected from the groupconsisting of peroxydisulfates and peroxymonosulfuric acid salts. Theperoxydisulfates can include those having the formula—N_(W)S₂O₈ where Nis an alkali metal or alkaline earth metal or ammonium, and w is 1 or 2.The alkali metal can include sodium, potassium or lithium. The alkalineearth metal can include calcium or magnesium. The persulfuric acid saltsinclude such compounds as KHSO₄.K₂SO₄ and 2KHSO₅ for example OXONE™.

The catalyst source for the non-halogen oxidizer is selected fromwater-soluble salts of copper and zinc ion donors. The source of copperion is a soluble salt, such as, copper sulfate, copper chloride, coppernitrate, copper bromide, copper flouride, copper metaborate, copperoxalate, copper acetate, copper citrate, copper gluconate, copperformate, copper salicylate, copper ammonium sulfate or mixture of thesewith each other or with other copper salts

The zinc ion can be provided by any water soluble zinc salts, such as,zinc sulfate (mono and heptahydrate), zinc chloride, zinc nitrate, zincbromide, zinc flouride, zinc iodide, zinc borate, zinc acetate, zinccitrate, zinc formate, zinc oxalate, zinc salicylate, zinc lactate ormixture of these with each other or with other zinc salts or anyrespective hydrates.

The clarifier material source can be sodium aluminum sulfate or otherchemicals used to treat the water system.

The optional boron source material may be any suitable compound ormixture, such as, disodium tetraborate decahydrate, disodium tetraboratepentahydrate, disodium tetraborate tetrahydrate, disodium octaboratetetrahydrate, sodium pentaborate pentahydrate, sodium metaboratetetrahydrate, sodium metaborate bihydrate, dipotassium tetraboratetetrahydrate, potassium pentaborate tetrahydrate, diammonium tetraboratetetrahydrate and ammonium pentaborate tetrahydrate. The optional boronsource material may also be selected from the group consisting of boricacid, boric oxide (anhydrous boric acid) and compounds having theformula M_(N)B_(X)O_(Y).ZH₂O, in which M=sodium, potassium, calcium,magnesium or ammonium, n=1 to 3, X=any whole number from 2 to 10,y=3x/2+1, z=0 to 14.

The water treatment composition comprises preferably 50 to 70%; morepreferably 55 to 65%, of halogen source material. The non-halogen oxygendonor source is preferably 5 to 40%, more preferably 8 to 25% of thecomposition, the boron source preferably constitutes 0 to 20%, morepreferably 0 to 10%, and the clarifier source is preferably 0 to 20%,more preferably 5 to 15%. The copper ion source is preferably 0.1 to10%, more preferably 0.5 to 5% and zinc ion source is preferably 0.5 to20%, more preferably 2 to 10%.

The invention is better understood using the following examples. Howeverthese examples are not to be interpreted as limiting the invention inany way. This invention is discussed in two parts—the first partcontains examples of peroxy salt catalysis by metal salts, and thesecond part contains examples of formulations containing peroxy salt,metal salt/s, chlorine oxidizer, clarifier and biocide.

I. Oxidation Performance of Sodium Dipersulfate

The following examples illustrate the oxidation performance of sodiumdipersulfate in the presence of transition metal salts, monitored bychange in crystal violet dye solution color. All experiments werecarried at ambient temperature.

The oxidation performance of the oxidizer or oxidizer based formulationswas determined by fading of the crystal violet dye solution color. Thefading of the color was monitored by measuring the UV absorbance of thedye solution at 589 nm, before and after addition of oxidizer oroxidizer based formulation. The change in absorbance or fading of colorof the dye solution, corresponds to the oxidation activity of theoxidizer. The greater the change in absorbance, more reactive is theoxidizer composition.

EXAMPLE 1

Examples 1a to 1e illustrate the effect of catalytic amount of coppersulfate pentahydrate on the oxidation performance of the sodiumdipersulfate at ambient temperature. The oxidation activity wasdetermined by measuring the destruction of crystal violet dye color at awavelength of 589 nm by these formulations.

-   Stock Solutions:-   Crystal Violet Dye solution: Prepare crystal violet dye solution by    dissolving 5 mg of crystal violet dye in 1000 mls of deionized    water. Dilute the solution accordingly to get a sharp peak at 589    nm.-   Sodium Dipersulfate solution: Prepare fresh stock solution by    dissolving 1 g of sodium dipersulfate in 100 mls of deionized water.-   Copper Sulfate solution: Prepare fresh stock solution by dissolving    1 g of copper sulfate pentahydrate in 100 mls of deionized water.-   Apparatus: HACH 4000 Spectrophotometer-   Procedure:    -   1. Prepare stock solutions of sodium dipersulfate (DPS) and        copper sulfate pentahydrate (CuSO₄.5H₂O) at different        concentrations as shown in Table 1.    -   2. Into 1500 mls beaker add 1000 mls of crystal violet dye        solution.    -   3. Using Hach spectrophotometer measure initial absorbance of        the dye solution at 589 nm.    -   4. From the stock solution add the molar amounts of DPS and        CuSO₄ in each beaker and allow the solution to stir for 1 and 2        hours.    -   5. Measure the absorbance at 589 nm after 1 and 2 hours reaction        time.    -   6. Calculate the percent decrease in crystal violet dye        absorbance at 589 nm using the formula:

${\%\mspace{14mu}{{Abs}.{Red}.}} = \left\{ {\frac{{Abs}_{i} - {Abs}_{f}}{{Abs}_{i}} \times 100} \right\}$

Where Abs_(i)=Absorbance of crystal violet dye solution at the start ofthe experiment

-   -   Abs_(f)=Absorbance of crystal violet dye solution at different        times after addition of stock solutions

The results are summarized in TABLE 1 and FIG. 1.

TABLE 1 Concentration, mM (milli Molar) Example Test Compd. 1a 1b 1c 1d1e DPS 1.0 1.0 1.0 1.0 1.0 CuSO₄.5H₂O 0.0 0.02 0.05 0.10 0.20 Absorbance(at 589 nm) 0 Hr 2.478 2.478 2.478 2.478 2.478 1 Hr 0.929 0.693 0.6790.650 0.633 2 Hr 0.609 0.43 0.414 0.420 0.375 % Reduction in Absorbance(at 589 nm) 0 Hr 0.0 0.0 0.0 0.0 0.0 1 Hr 62.5 72.0 72.6 73.8 74.5 2 Hr75.4 82.7 83.3 83.1 84.9

The results of example 1a show the oxidation performance of 1 mMsolution of sodium dipersulfate in absence of copper ions. In subsequentexamples 1b to 1e, dipersulfate concentration was kept constant at 1 mMwhile increasing the copper sulfate concentration from 0.02 mM to 0.20mM. Under the conditions of test performed, these results indicate thatthe oxidation performance of sodium dipersulfate is increased inpresence of a very small amount of copper sulfate after 1 and 2 hours ofreaction time. Very small change in oxidation activity is observed byincreasing the copper sulfate concentration as indicated by examples 1cto 1e. Based on this study it is concluded that only a small amount ofcopper ions from a solid copper salt material is required to increasethe oxidation of sodium dipersulfate in solution.

EXAMPLE 2

In this example the effect of zinc sulfate heptahydrate on oxidationperformance of sodium dipersulfate was determined by measuring thedestruction of crystal violet dye color at 589 nm.

-   Reagents:-   Crystal Violet Dye solution: Prepare stock solution as described in    example 1.-   Sodium Dipersulfate solution: Prepare stock solution as described in    example 1.-   Zinc Sulfate solution: Dissolve 10 g of Zinc Sulfate Heptahydrate in    100 mls of deionized water.-   Apparatus: HACH 4000 Spectrophotometer-   Procedure:    -   1. Prepare stock solutions as shown in Table 2    -   2. Follow the steps 2 to 6 as outlined in procedure for example        1.

The results are summarized in Table 2 and FIG. 2.

The results of example 2a (control) shows the oxidation of crystalviolet dye solution by 1 mM sodium dipersulfate solution at ambienttemperature. In the following examples 2b to 2d, concentration of zincsulfate heptahydrate was varied from 0.5 to 5.0 mM while keeping thedipersulfate concentration constant at 1 mM. The results of example 2ato 2d indicate that zinc sulfate has no effect on the oxidationperformance of sodium dipersulfate.

TABLE 2 Test Compd. Concentration, mM Example 2a 2b 2c 2d DPS 1.0 1.01.0 1.0 ZnSO₄.7H₂O 0.0 0.5 1.0 5.0 Absorbance (at 589 nm) 0 Hr 2.5292.529 2.529 2.529 1 Hr 0.871 0.928 0.927 0.889 2 Hr 0.446 0.512 0.5120.489 % Red. Absorbance (at 589 nm) 0 Hr 0.0 0.0 0.0 0.0 1 Hr 65.6 63.363.4 64.9 2 Hr 82.4 79.8 79.8 80.7

EXAMPLE 3

In these experiments oxidation performance of the sodium dipersulfate inthe presence of catalytic amount of copper sulfate pentahydrate and zincsulfate heptahydrate was determined by measuring the destruction ofcrystal violet dye solution at 589 nm.

-   Reagents:-   Crystal Violet Dye solution: Prepare stock solution as in example 1.-   Sodium Dipersulfate solution: Prepare stock solution as in example    1.-   Copper Sulfate solution: Prepare stock solution as in example 1.-   Zinc Sulfate solution: Prepare stock solution as in example 2.-   Apparatus: HACH 4000 Spectrophotometer-   Procedure:    -   1. Prepare the solutions at different concentrations as shown in        Table 3.    -   2. Follow the steps 2 to 6 as outlined in procedure for example        1.

The results are summarized in Table 3 and FIG. 3.

TABLE 3 Concentration, mM Example Test Compd. 3a 3b 3c 3d 3e 3f DPS 1.01.0 1.0 1.0 1.0 1.0 CuSO₄.5H₂O 0.0 0.03 0.03 0.03 0.03 0.03 ZnSO₄.7H₂O0.0 0.00 0.03 0.06 0.30 0.60 Absorbance (at 589 nm) 0 Hr 3.106 3.1063.106 3.106 3.106 3.106 0.5 Hr 1.496 1.189 1.146 1.085 1.027 0.996 1 Hr0.998 0.784 0.793 0.761 0.725 0.739 3 Hr 0.483 0.403 0.391 0.390 0.3710.387 % Red. Absorbance (at 589 nm) 0 Hr 0.0 0.0 0.0 0.0 0.0 0.0 0.5 Hr51.8 61.7 63.1 65.1 66.9 67.9 1 Hr 67.9 74.8 74.47 75.5 76.7 76.2 3 Hr84.5 87.0 87.4 87.4 88.1 87.5

Examples 3a to 3f demonstrate the synergistic activity of copper andzinc ions in catalyzing the oxidation of sodium dipersulfate solution atambient temperatures. Example 3a is the control showing the oxidationperformance of 1 mM solution of sodium dipersulfate. In Example 3b to3f, sodium dipersulfate concentration was kept constant at 1 mM andcopper sulfate at 0.03 mM. The zinc sulfate concentration was increasedfrom 0.00 to 0.60 mM in these experiments. The results indicate that thecopper sulfate and zinc sulfate have a synergistic effect on theoxidation performance of sodium dipersulfate. So, for example 0.3 mM ofzinc sulfate along with 0.03 mM of copper sulfate (0.5 hour) provides asynergistic oxidation activity that is better than that obtained bydipersulfate alone or dipersulfate activated by copper sulfate or zincsulfate.

II. Oxidation Performance of Formulations Containing SodiumDipersulfate, Metal Salts, Chlorine Oxidizer, Clarifier and Biocide

The following examples clearly illustrates the benefit of using twotransition metal salts to increase the oxidation performance of theformulations containing sodium dipersulfate, sodium dichlor, alum andborax.

EXAMPLE 5

The oxidation performance of the four formulations 5a, 5b, 5c and 5dwith or without catalytic amount of copper sulfate pentahydrate, zincsulfate heptahydrate or copper sulfate+zinc sulfate, respectively wasdetermined by method as described in example 1. Table 4 enlists thecompositions of these example formulations that can be used in treatmentof recreational water systems like swimming pools, spas etc.

TABLE 4 Form Form Form Form Chemicals 5a % 5b % 5c % 5d % Sodiumdichloro-s- 55.0 55.0 55.0 55.0 Triazinetrione Sodium dipersulfate 23.023.0 23.0 23.0 Sodium tetra borate pentahydrate 10.0 10.0 10.0 10.0Aluminum sulfate 12.0 11.5 9.0 5.7 Copper sulfate pentahydrate 0.0 0.500.0 0.30 Zinc sulfate heptahydrate 0.0 0.0 3.0 6.0

1% stock solution of formulations 5a, 5b, 5c and 5d was prepared indeionized water and 0.5 mls of this stock solution was added to 1 literof crystal violet dye solution to give 5 mg/l of product concentration.The oxidation performance of the formulations as indicated by the %decrease in absorbance at 589 nm with time is shown in FIG. 4.

The results of these experiments validates the findings documented inexample 1 (1a to 1e), example 2 (2a to 2d) and example 3 (3a to 3f).Formulation 5b containing small amount of copper sulfate pentahydrateshows better oxidation than control formulation 5a, having no metalcatalysts. Zinc Sulfate has no effect on the oxidation performance ofthe formulation as can be seen by the results of formulation 5c.However, formulation 5d containing both copper sulfate and zinc sulfateclearly shows the best oxidation performance amongst all theformulations listed in Table 4.

EXAMPLE 6

The oxidation performance of the two formulations J and K in presence ofcatalytic amount of copper sulfate and copper sulfate+zinc sulfate,respectively was determined by method as described in example 1. Theseformulations to be used in treatment of recreational water systems likeswimming pools, spas etc have the compositions shown in Table 5.

TABLE 5 Form. J Form. K Chemicals % % Sodium dichloro-s- 65.0 65.0Triazinetrione Sodium dipersulfate 20.0 20.0 Sodium tetra boratepentahydrate 4.0 2.0 Aluminum sulfate 10.0 8.0 Copper sulfatepentahydrate 1.0 1.0 Zinc sulfate heptahydrate 0.0 4.0

1% stock solution from formulation J and K was prepared and 0.5 mls ofthis stock solution was added to 1 liter of crystal violet dye solutionto give 5 ml/l of product concentration. The oxidation performance ofthe formulations as indicated by the % decrease in absorbance with timeis shown in FIG. 5.

The results of these experiments clearly indicate better oxidationperformance of formulation containing both copper sulfate and zincsulfate as catalysts as compared to only copper sulfate.

Further variations and modifications of the invention will be apparentto those skilled in the art from the foregoing and are intended to beencompassed by the claims appended hereto.

1. A process for the treatment of recirculating water by adding theretoa composition comprising sodium dipersulfate, 0.5 to 5% by weight basedon the composition of copper sulfate or copper citrate and 2 to 10% byweight based on the composition of zinc sulfate which providessynergistic oxidation activity in the presence of an oxidizingsanitizer.
 2. The process according to claim 1, wherein the oxidizingsanitizer present in the water is a source of hypochlorous acid.
 3. Theprocess according to claim 1, wherein the combination is copper sulfatepentahydrate or copper citrate in an amount of from 0.5 to 5% by weightof the composition, and zinc sulfate heptahydrate in an amount of 2 to10% by weight of the composition.
 4. A composition of matter comprisingsodium dipersulfate and copper sulfate or copper citrate and zincsulfate, wherein the copper sulfate or citrate is present in an amountof 0.5 to 5% by weight of the composition and the zinc sulfate ispresent in an amount of 2 to 10% by weight of the composition.
 5. Amethod for improving the activity of a peroxy compound in a compositioncontaining sodium dipersulfate comprising adding to the composition anamount of copper sulfate or copper citrate and zinc sulfate to provide acomposition containing from 0.5 to 5% by weight of the composition ofcopper sulfate or citrate, and from 2 to 10% by weight of zinc sulfate.6. A sanitizing composition comprising a mixture of a halogen sourcematerial, sodium dipersulfate and a combination of copper and zinctransitional metal ions as a catalyst source wherein copper is presentas copper sulfate or copper citrate in an amount of 0.5 to 5% by weightof the composition and zinc is present as zinc sulfate in an amount of 2to 10% by weight of the composition.
 7. The composition of claim 6, inwhich the halogen source material is sodium or potassium dichlor,tricolor, calcium hypochlorite and/or lithium hypochlorite.
 8. Thecomposition of claim 6, in which boron is an optional component.
 9. Thecomposition of claim 8, where a boron source material is selected fromthe group consisting of boric acid, boric oxide (anhydrous boric acid)and compounds having the formula M_(N)B_(X)O_(Y).ZH₂O, in whichM=sodium, potassium, calcium, magnesium or ammonium, n=1 to 3, X=anywhole number from 2 to 10, y=3x/2+1, z=0 to
 14. 10. The composition ofclaim 9, wherein the boron source material is present in amount up to20% by weight of the composition.
 11. The composition of claim 6, inwhich a clarifier source material is present for water treatment. 12.The composition of claim 11, in which the clarifier source material isaluminum sulfate or sodium aluminum sulfate.
 13. The composition ofclaim 12, wherein the aluminum sulfate or sodium aluminum sulfate sourcematerial is present in amount of up to 20% by weight of the composition.14. A composition of matter for the treatment of a water system toinhibit growth of micro-organisms comprising sodium dipersulfate and asa catalyst a combination of 0.5 to 5% by weight based on the compositionof copper sulfate or copper citrate and 2 to 10% by weight based on thecomposition of zinc sulfate to improve the oxidation properties of thesodium dipersulfate at ambient temperature.